USE OF DICARBONYL COMPOUNDS TO INCREASE THE
THERMAL STABILITY OF BIOPOLIMEROS IN THE FIELD OF THE
EXPLORATION OF PETROLEUM AND NATURAL GAS
DESCRIPTION OF THE INVENTION The present invention relates to the use of dicarbonyl compounds to increase the thermal stability of biopolymers in aqueous liquid phases that are used in the field of petroleum and natural gas exploration. Biopolymers, in particular those of fermentative origin such as, for example, sclerogucane, xanthan gum, succinoglycan, diutane or welan gum, are widely used to form viscosity in aqueous liquid phases; for example, in cosmetic compounds or in general in the food industry. Regardless of the various fields of use, thinning by thixotropic cutting and / or thickening of the respective liquid phase is often of paramount importance. Among the industrial applications of biopolymers, the rheological control of drilling fluids used to explore natural oil and gas reserves should be mentioned first. The person skilled in the art knows that in particular the drilling fluids that thin by cutting promote in a very efficient way the removal of the well from the cuttings of the cut.
trepan. In detail, biopolymers play a different role in different drilling applications. In addition to the aforementioned improvement of the drag capacity in combination with a good ease of pumping, the fluids based on biopolymers that thin with the cut also reduce the loss of fluid, stabilize the soil formations and promote an easy separation of the cuts of the circulating drilling fluid. In practice, biopolymers are used particularly frequently as thickeners for solid-free drilling fluids, so-called "inlet fluids". In contrast to aqueous clay suspensions, "inlet fluids" based on biopolymers prevent damage to the formation of the deposit, ultimately resulting in higher productivity of the oil or natural gas well. In addition, bipolymers are often an essential constituent of the so-called "spacer fluids" that are used in the return for the cementation of the well in order to ensure an optimal bond of the cement to the well wall. According to this wide range of applications, in the present context, "aqueous liquid phases" are also understood as those which, in addition to fresh water or salt water, may contain a number of additional principal or secondary components; this
it also includes salt-containing systems (so-called "brines") and more complex drilling fluids such as, for example, emulsions or inverse emulsions which may also contain large proportions of an oil component. According to prior art to date, only certain biopolymers are suitable for common high temperature applications in the range of > 121.1 ° C which are completely customary in the exploration of oil and natural gas. Scleroglucan and welan gum can be mentioned first here. In comparison with xanthan gum, these special polysaccharides generally have a substantially higher thermal stability which, depending on the conditions of use, is usually 10 to 37.8 ° C above the xanthan gum limit. Additionally, the rheological performance of comparatively inexpensive xanthan gum generally decays dramatically, even at temperatures substantially lower than 121.1 ° C (generally 71.1 ° C). Even before the thermal degradation of the xanthan gum molecules occurs, the structural viscosity is thereby "spontaneously" reduced as a result of Brownian molecular motion. In principle, the degradation of the biopolymer chains and their viscosity-generating properties
It takes place in the course of time and as a function of the temperature profile in the course of drilling. The exact composition of the liquid phase is also important. For example, it is known that high salt contents increase the harmful effects while small doses of certain salts have a limited stabilizing influence. In practice, so-called "oxygen separators" or reducing agents are often used, such as, for example, sodium sulphite, sodium bisulfite or formate salts. Furthermore, it is known that so-called redox catalysts or free radical mediators such as, for example, Fell, CoII or Nill promote the action of said "oxygen separators". Presumably its presence is even absolutely essential for the mechanism of action of the redox reaction with dissolved oxygen. The use of amines as "thermal extension agents" for hydroxyethylcellulose (HEC) has already been described in WO 02/099258 Al, wherein use in combination with xanthan gum is also mentioned. It remains to be said that these stabilizers always have only gradual effects, which only results in a relative improvement depending on the biopolymer used. This means in the first place that xanthan gum does not reach the level of the other biopolymers listed even in the presence of the stabilizers according to
the prior art. However, in the second place this also means that there are also higher temperature limits for these "relatively high quality" biopolymers, such as scleroglucan and welan gum. This should be considered in conjunction with the tendency to always drill deeper into the search for oil or natural gas, so that the drilling fluid must withstand higher and higher temperatures. WO 2005/061652 A1 relates to drilling fluids containing a polymer as an agent that provides viscosity with enhanced thermal stability. This characteristic is achieved by compounds having two acid functions, for example, sodium oxalate. The polymeric component is a water-soluble polymer, wherein polyacrylamides, celluloses, cellulose derivatives, sclerogucan polysaccharides, xanthan polysaccharides and other biopolymers are mentioned. In this context, biopolymers which are dicarbonic acids are of particular importance. US 5,612,294 relates to drilling muds containing scleroglucan. As a side effect it is described that modified compounds can be used as suitable scleroglucan components
additional, which can be obtained, for example, by treating the scleroglucan with a dialdehyde reagent such as, for example, glyoxal. In addition, it is described that these sludges have a wide range of application, with preference being given to drilling at high temperatures of up to 120 ° C. In the case of higher temperatures, an irreversible gelation occurs as an indicator of degeneration. It is further disclosed that the biopolymer component is converted exclusively via a dialdehyde reagent. Finally it is revealed that degeneration processes occur at a temperature above 120 ° C. A method for influencing the gelation time of aqueous gels of organic crosslinking in the underground formations is disclosed in US 5,617,920. Examples of the polymer capable of crosslinking underground that is used are also polymers such as cellulose ether, polysaccharides and lignosulfonates. These polymers can be converted by organic crosslinking agents such as, for example, dialdehydes and glyoxal. The document does not contain any indication in the sense that these modified polymers have enhanced thermal stability. According to US Pat. No. 4,350,601, viscosity-promoting compounds are used as additives in brines with a high zinc salt content. The promoters
of viscosity are obtained by conversion of polysaccharides, among other things with dialdehydes. It is of particular interest to improve the dispersion characteristics and the viscosity of the biopolymer component, which, however, does not result in enhanced thermal stability. The drilling and well service fluid described in DE 698 18 148 A1 comprises a biopolymer viscosity promoter and, inter alia, an aqueous salt solution containing formate salts dissolved therein. It is generally stated that it is known that the use of formate salts enhances the thermal stability of certain aqueous solutions containing polysaccharides; in this context, reference is made to document US 4,900,457. The term "biopolymer" is defined as extracellular polysaccharide having a high molecular weight greater than 500,000. It is further stated that the fluid of the invention can have excellent thermal stability. From US 2004/0138069 a drilling fluid is known which comprises inter alia a polysaccharide and a cellulose derivative in addition to the primary fluid. DE 37 85 279 A1 describes, among other things, the thermal stability of aqueous polysaccharide compounds which can be improved in particular by adding
specific formic acids. It was therefore the object of the present invention to provide novel compounds for increasing the thermal stability of biopolymers in aqueous liquid phases in the exploration of petroleum and natural gas. Each increase in the upper temperature limit and the associated extent of the possible range of applications should be considered as a substantial progress from the point of view of the expert in the field. This object was achieved by the use of dicarbonyl compounds in temperature ranges > 71.1 ° C. Unexpectedly it was discovered that dicarbonyl compounds are capable of increasing the thermal stability of biopolymers simultaneously at high temperatures. Therefore, a marked effect is obtained even with the simple binary mixture of biopolymers and dicarbonyl compounds, for example, scleroglucan and a dialdehyde. However, an extension of the upper temperature limit is obtained by combining with a stabilizer known as, for example, sodium bisulfite. This effect of the dicarbonyls is all the more surprising since, due to their chemical structure and possible reactions, these compounds can not be assigned to the known category of reducing agents or "separators".
of oxygen "and do not act as pH regulators in the sense of the amines mentioned above, it should be assumed that dicarbonyl in general and glyoxal in particular form acetals and hemiacetals with the ROH groups of polysaccharide biopolymers. it is known that this leads to the better solubility of biopolymers, however, this does not result in a logical starting point for a mechanical explanation of the best thermal stability, and it is for this reason that the claimed effect is all the more surprising. The biopolymers according to the invention are molecules formed from a multitude of biomolecules which are monomers, in particular at least three, preferably at least five and in particular at least ten and more preferably at least twenty monomers. are, for example, polysaccharides, that is, biopolymers formed of sugars that are monomers, polypeptides or proteins, is say, biopolymers formed of amino acids that are monomers. The use of a polysaccharide as a biopolymer is particularly preferred. In particular, the biopolymer component according to the present invention should preferably be a polysaccharide prepared by fermentation, being considered as particularly
Suitable elements of the series consisting of scleroglucan, welan gum, diutane, ramzano and succinoglycan. The aqueous liquid phases according to the invention are systems which are liquid and have a water content of at least 10% by weight, more preferably at least 50% by weight and particularly preferably at least 80% by weight. In connection with the oil and natural gas exploration applications essential for the invention, those aqueous liquid phases which constitute a drilling fluid are particularly suitable. It is noted that the observed effect of the increase in thermal stability is particularly pronounced in the case of dicarbonyls if this drilling fluid preferably contains fresh water and / or salt water from the sea. In a particularly preferred manner, it should be a salt-containing system of the "brine" type. However, the present invention also includes a variant in which the drilling fluid is an emulsion containing oil or an inverted emulsion. The dicarbonyl compounds according to the invention are any compounds containing at least two carbonyl groups, specifically C = 0 groups. From the series of dicarbonyl components
suitable for carrying out the thermal stability increase of the biopolymers, dialdehydes such as malonaldehyde CH2 (CHO) 2 were found to be particularly suitable., succinic aldehyde C2H4 (CHO) 2, glutaraldehyde C3H6 (CHO) 2 and preferably the simplest member, glyoxal CHOCHO. Additionally, certain diketones, such as, for example, dimethylglyoxal (COCH3) 2 or acetylacetone CH2 (COCH3) 2, are also claimed as typical members of the dicarbonyls in the context of this invention. However, preferred dicarbonyl components are also dicarboxylic acids and their derivatives, specifically salts, esters and ethers. In total it should be said that the compounds having neighboring carbonyl groups were found to be particularly suitable. However, in addition to these α-dicarbonyl compounds also the β-dicarbonyl compounds such as, for example, malonic acid also satisfy the purpose according to the invention. The present invention also comprises that the dicarbonyl component is added by mixing it with the liquid phases independently of its chemical composition, although a variant in which the dicarbonyl component is incorporated into the biopolymer in the course of the preparation of this biopolymer is considered to be particularly preferred. .
The effect according to the invention of the dialdehyde component, specifically the increase in thermal stability can be further increased if in addition to the dicarbonyl component other compounds are used which serve to stabilize the drilling fluid, in particular to the biopolymers present therein and especially to increase the thermal stability of the same. From the series of suitable compounds, "oxygen scavengers" such as, for example, lignosulfonates and tannates may be mentioned at this point in particular. Sodium sulfite, sodium bisulfite or formates, ie, formic acid salts which are generally known as reducing agents (cf. "Composition and Properties of Drilling and Completion Fluids", 5. Edition, Darley HCH) are also preferably suitable. &Gray GR, Gulf Publishing Company, Houston, Texas, pages 480-482). However, primary, secondary and tertiary amines, and in particular triethanolamine, are also suitable. It should also be noted that the performance of these "oxygen scavengers" or radical scavengers such as, for example, sodium sulfite can be further markedly increased by Fell, Nill or CoIII salts. These salts presumably act as
mediators of free radicals and therefore catalyze the binding of free oxygen radicals. The use according to the invention is in principle not linked to any defined temperature range, but the thermal stability effect is particularly pronounced if the temperatures in the rock formation are > 121.1 ° C, preferably > 135 ° C and particularly preferably > 148 ° C. In sum, it remains to be said that dicarbonyls are unexpectedly excellently suited to increase the thermal stability of biopolymers in aqueous liquid phases used in the exploration of oil and natural gas. Therefore, the success of the use according to the invention is all the more unexpected because the compounds having dicarbonyl characteristics can not be assigned to the classes of compounds known to date which are already known to increase markedly the thermal stability of biopolymers. The invention relates to the use of dicarbonyl compounds to enhance the thermal stability of biopolymers in aqueous liquid phases in the field of oil and natural gas exploration in temperature ranges > 71.1 ° C, particularly > 82.2 ° C, preferably > 93.3 ° C, more preferably > 121. IoC, still more preferably 135 ° C and mostly
preferred > 148.9 ° C. The biopolymer components are preferably polysaccharides produced in fermentative form such as, for example, scleroglucan or welan gum. The aqueous liquid phase is typically a drilling fluid which may also contain high concentrations of salt ("brines"). A particularly suitable representative of the dicarbonyls is glyoxal. The glyoxaεl can either be added to the liquid phase or preferably added during the preparation of the biopolymer. The use according to the invention shows its advantages in particular at temperatures in the geological formation exceeding 121.1 ° C. The following examples illustrate the advantages of the claimed use. Examples The properties of the respective drilling fluids were determined according to the methods of the American Petroleum Institute (API), standard RP13B-1. Therefore the rheologies were measured using an appropriate FA 35 viscometer at 600, 300, 200, 100, 6 and 3 revolutions per minute (rpm). As is known, measurements at slow speeds of 6 and 3 rpm are particularly relevant with respect to the structural viscosity and drag capacity of the fluids. In addition to this, the so-called "slow-cut rheology" was also determined
using a Brookfield viscometer HAT at 0.5 rpm. Specifically, the measurements were conducted and each case before and after a heat treatment ("degeneration") for 16 hours in a roller furnace conventional in the industry at the temperatures indicated in each case. Example 1: The increase in thermal stability of an aqueous solution of scleroglucan containing salt by glyoxal is described. The scleroglucan component used was the BIOVIS® product of Degussa Construction Polymers GmbH (comparative); in the experiments according to the invention, the BIOVIS® product contained an amount < 1% glyoxal ("+ G") in addition to scleroglucan. Preparation of drilling fluids: Initially, 350 ml of a saturated aqueous solution of NaCl (109 g of NaCl and 311 g of water) were introduced at a "slow" speed into a Hamilton Beach mixer (HBM) conventional in the industry. After this, 3.5 g of the respective BIOVIS® component and 1 g of sodium sulfite (stabilizer) and 1 ml of tributylphosphate (antifoam) were added. After stirring for 20 minutes in the HBM the rheology was measured at a temperature of 60 ° C (BHR = before hot grinding). Additional rheology measurements were carried out at 60 ° C after
a thermal load of 16 hours at the degeneration temperatures of 148.9 ° C to 176.7 ° C indicated in each (AHR = after hot grinding). Results: Table 1:
First, the data make it clear that moderate temperatures of up to 149 ° C even improve the rheological performance of scleroglucan. However, this is merely a hydration effect in "brines"
saturated with salt; that is, the biopolymer is completely dissolved only by thermal conditioning. This subsequent dissolution is less pronounced in the case of BIOVIS® + G (invention) by virtue of which this type containing glyoxal is very well soluble from the start and at normal ambient temperatures. Finally, the additional experimental series at demanding temperatures of 148.9 ° C to 176.7 ° C proves the improvement of thermal stability by the presence of a glyoxal that is discovered according to the invention. Example 2: The increase in thermal stability is described by the glyoxal of an aqueous solution of scleroglucan loaded with calcium chloride. The scleroglucan component used was the BIOVIS® product from Degussa Construction Polymers GmbH (comparative); in the experiments according to the invention, the BIOVIS® product contained an amount < 1% glyoxal ("+ G") in addition to scleroglucan. Preparation of drilling fluids: Initially, 350 ml of an aqueous solution containing CaCl2 (155 g of CaCl2 and 307 g of water) was introduced at a "slow" speed in a Hamilton Beach industrial mixer (HBM). After this, 3.5 g of the respective BIOVIS® component and 1 g were added.
of sodium sulfite (stabilizer), 0.25 g of FeIIS04 as a mediator of free radicals and 1 ml of tributyl phosphate (antifoam). After stirring for 20 minutes in the HBM the rheology was measured at a temperature of 60 ° C (BHR = before hot grinding). Additional rheology measurements were carried out at 60 ° C after a thermal load of 16 hours at the degeneration temperatures of 148.9 ° C to 176.7 ° C indicated in each case (AHR = after hot grinding). Results: Table 2: Measurement Brine Rheology FANN 35 Rheology CaCl2 (60 ° C) at Brook-Density 600-300-200-100-6-3 field 1.32 kpl rpm HAT a (kg / liter) (kg / 9.29 m2) 0.5 rpm (mPas)
BIOVIS® BHR 24.5- 18.6-15.88-13.6-8.6-7.7 44640 BIOVIS® + G BHR 23.6-17.7-15.88-13.15-9.07-7.7 48320
BIOVIS® AHR® 149 ° C 19.96-17.24-15.42-13.15-7.26-5.9 41120 BIOVIS® + G AHR® 149 ° C 21.77-18.14-16.78-14.51-9.53-8.16 46560
BIOVIS® AHR® 163 ° C 14.51-10.89-9.07-6.8-2.27-1.36 5000 BIOVIS® + G AHR® 163 ° C 20.4-17.7-16.78-14.51-9.07-7.7 46240
BIOVIS® AHR® 177 ° C 7.7-5.9-4.54 -3.18 -0.45-0.45 0 BIOVIS® + G AHR® 177 ° C 19.5-15.42-13.6-10.89-5.44-4.54 19480
Again, the data, particularly at very demanding temperatures above 148.9 ° C, prove the improvement of thermal stability by the addition of glyoxal which was discovered according to the invention. Example 3: The increase in thermal stability of an aqueous welan gum solution is described by the addition of glyoxal. The welan rubber component used was the BIOZAN® product from CP Kelco. The glyoxal was used in the form of a 40% aqueous solution obtained commercially. In addition, the fluid was contaminated by the addition of a cement slurry that had just been prepared in order to simulate the conditions of use as "spacer fluid". Preparation of drilling fluids: Initially, 350 ml of water was introduced at a "slow" speed into a conventional Hamilton Beach (HBM) industrial mixer in the industry. 3.5 g of BIOZAN® and 1.0 g of Na2S03 (stabilizer) and 1 ml of tributylphosphate (antifoam) were added. To one of the two batches of this type that were prepared simultaneously, 0.35 ml of glyoxal solution (invention) was added. After this, 50 g of a cement slurry (consisting of 800 g of Lafarge H-type cement and 304 g of water, intermixed in advance for 20 minutes in a
atmospheric consistometer at 60 ° C). After stirring for 20 minutes in the HBM the rheology was measured at a temperature of 60 ° C (BHR = before hot grinding). Additional rheology measurements were carried out after a thermal load of 4 hours at 148.9 ° C (AHR = after hot grinding). Results: Table 3:
Again the data prove the improvement of thermal stability by the addition of glyoxal which is discovered according to the invention.